1. Field of the Invention
The present invention relates to surface mount electrical component packaging technology, and, more specifically, to a surface mount power module dual footprint device and its method of manufacture.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Electronic device manufacturers face tremendous pressure to make devices small, yet inexpensive. With the advent of surface mount packaging technology this goal has been realized. Surface mount technology (SMT) has evolved to allow Printed wiring assemblies (PWA) to be very high density configurations. By utilizing standard SMT devices and printed circuit boards (PCB) or printed wiring boards (PWB), electrical designs can be made more efficient and costs can be reduced.
Some electrical designs require the use of power converter modules. These power converter modules are discrete components which are assembled to PWA. The majority of power converter modules utilize through-hole mounting technology to form the connection to the PCB. Using a power converter module that utilizes through-hole connections to a PWB having a majority of SMT components increases the number of manufacturing steps required for the PWA. This increase in the number of manufacturing steps increases the overall cost of the final PWA.
To reduce the manufacturing steps associated with through-hole mounted power converter modules on a PWA with a majority of SMT components, surface mount peripheral leaded power converter modules, such as gull-wing and J-lead, were introduced. With this evolution, the size of the power converter modules occupied more space on the PWB. To address this problem, the leads were moved beneath the power converter module. Specialized manufacturing techniques, tools, and equipment are required to successfully utilize this package design in the PWA manufacturing process. The use of connections beneath the power converter module increases the difficulty of inspecting the connections and reworking this device, if necessary. Stand-off components may be added to the power converter module to assist with visual inspection. However, stand-off or spacer components add to the overall height of the device and may create further interference with other components. Furthermore, the added stand-off components increase the overall material and manufacturing cost of the power converter modules.
Specialized sockets for accepting the power supply package were also developed to allow easy placement and removal of a power converter module with bottom leads. These specialized sockets may be more easily mounted and soldered to the PWB. Once properly mounted, the power converter module may simply be plugged into the socket. However, this extra component again adds to the overall power supply height and increases the costs associated with design and manufacture of the PWA.
FIG. 1 and FIG. 2 each depict a power converter module mounting standard as proposed by the Distributed-Power Open Standards Alliance (DOSA). Instead of using the peripheral leaded design, the solder joints are located beneath the component. As previously mentioned, this placement of the solder joint connections beneath the device increases the manufacturing, inspection and repair process costs. Pins or stand-offs may be utilized to raise the power converter module to assist with visual inspection, but again this adds to the overall height and cost of the power converter module.
A properly formed solder joint is necessary for reliable electrical and mechanical connection of the power converter module to the PCB. The solder joints of the SMT power converter module are formed during the solder reflow manufacturing process. During the solder reflow process, the solder alloy must reach its melting point temperature to create the connection between the pads on the power converter module and the pads of the PCB. In order to reach the necessary solder melting point temperature beneath the power converter module, devices of lower thermal mass located on the PCB may become overheated.
The solder joints, of the power converter module, located beneath the device should be inspected to qualify their mechanical and electrical integrity. In the event that the power converter module must be removed from the PWA, specialized process, tools, and equipment may be required to melt the solder joints beneath the device. During the removal process, failure analysis evidence may be destroyed.
Second sourcing electronics devices is a typical purchasing practice in the electronics industry. A PWA manufacturer may desire a second source for power module converters in order to stimulate competitive pricing, alleviate component shortages, and lessen the risk of relying on one supplier. To accommodate the second source strategy, a PCB design may be modified to accommodate the use of two different mounting designs, such as through-hole and surface mount.
Accordingly, an alternative solder joint connection design for power converter modules is needed to facilitate ease of PWA manufacture, inspection and rework, and to reduce material cost. The present invention satisfies these needs and others as shown in the following detailed description and accompanying drawings.